We have two, 20' conex on the property. We had the driver set them on 4x4s to distribute the weight and keep them off the dirt.
I cut an 8" hole towards the top of one door on each conex and mounted a solar powered fan inside, roof vent outside for rain, solar panel flat on the roof.
They stay dry and some rolled on Henry"s white roof seal helps drop the temperature inside.

"Camping places fix themselves in your mind as if you had spent long periods of your life in them.
You will remember a curve of your wagon track in the grass of the plain like the features of a friend."
Isak Dinesen